This improved invention provides a better means to achieve low cost affordable solar energy. It does so by greatly increasing the concentration factor over that which was hitherto possible, and hence further reducing the cost of solar concentrators which increase (concentrate) the density of solar energy incident on a solar energy converter. The utilization of solar energy has been encumbered by the high cost of energy converters such as photovoltaic solar cells. For example, this invention makes it possible to replace an even larger number of expensive solar cells with a small number of solar cells operating in conjunction with the inexpensive intelligent micro-optics of this invention. Thus the instant invention can contribute to the goal of achieving environmentally clean energy on a large enough scale to be competitive with conventional energy sources.
A limiting factor in U.S. Pat. No. 6,612,705, of which the inventor of this instant invention is a co-inventor, is that it is dificult to achieve a concentration greater than 10× because the mirrored balls are not closely enough confined between two sheets, permitting some lateral motion between the two sheets of that Patent. In that issued Patent, the balls have too large a translational degree of freedom, which problem is solved by the instant invention. The instant invention overcomes this problem by much more closely confining each mirrored ball in an individual cavity within a single sheet. Another problem of the issued U.S. Pat. No. 6,612,705, is that of having higher friction than can be readily tolerated, which also limits the exacting alignment required by the mirrored balls for concentrations much greater than 10×. The instant invention also overcomes the friction problem.
The 1978 Gyricon U.S. Pat. No. 4,126,854 of Sheridon, entitled “Twisting Ball Panel Display” is exclusively concerned with Displays. There is no mention of any other application than Displays, either specifically or by general statement. In this and other Sheridon patents, no mention is made of a mirror in the gyricon balls, nor is there any mention of specular reflection as would be obtained from a mirror. On the contrary, diffuse reflection needs to be increased from the balls so the Gyricon display may easily be observed from all angles. Certainly there is no anticipation of a solar concentrator application, solar propulsion assist, optical switching or any other micro-mirror application. Furthermore, a uniform monolayer(s) of micro-mirrored balls are preferred in these applications, whereas the Sheridon patent and related patents only teach a random dispersion of non-mirrored Gyricon balls.
The instant invention is primarily concerned with solar concentrator micro-mirrors in cavities in a single sheet, rather than two sheets, for more accurate alignment and for nearly frictionless rotation. However, it has broader applications wherever focusing planar mirrors are used for applications such as for solar propulsion assist and optical switching. In the instant invention the micro-mirrors can be either pre-formed (pre-existing), or formable in-situ.
Definitions
“Concentrator” as used herein in general is a micro-mirror system for focusing and reflecting light. In a solar energy context, it is that part of a Solar Collector system that directs and concentrates solar radiation onto a solar Receiver.
“Dielectric” refers to an insulating material in which an electric field can be sustained with a minimum power dissipation.
“Elastomer” is a material such as synthetic rubber or plastic, which at ordinary temperatures can be stretched substantially under low stress, and upon immediate release of the stress, will return with force to approximately its original length. Silicone elastomers have exceptional ability to withstand ultraviolet light degradation.
“Electret” refers to a solid dielectric possessing persistent electric polarization, by virtue of a long time constant for decay of charge separation.
“Focusing planar mirror” is a thin almost planar mirror constructed with stepped varying angles so as to have the optical properties of a much thicker concave (or convex) mirror. It can heuristically be thought of somewhat as the projection of thin equi-angular segments of small portions of a thick mirror upon a planar surface. It is a focusing planar reflecting surface much like a planar Fresnel lens is a focusing transmitting surface. If a shiny metal coating is placed on a Fresnel lens it can act as a Fresnel reflector.
“ITO” is a thin conducting alloy of Indium/Tin Oxide that is transparent.
“Packing fraction” herein refers to the fraction of an available area occupied by the collection (ensemble) of rotatable elements.
“Plasticizer” as used herein refers specifically to a dielectric plasticizer fluid that is absorbed by an elastomer thereby causing it to swell thus creating a spherical shell around each of the micro-mirror balls which do not substantially absorb the plasticizer. More commonly plastizers are added to a material to make it softer, more flexible, or more moldable.
“Receiver” as used herein in general is a system for receiving reflected light. In a solar energy context, it receives concentrated solar radiation from the micro-mirror assembly for the conversion of solar energy into more conveniently usable energy such as electricity.
“Silicone” as used herein refers to a heat-stable, rubber-like elastomer that is a water repellent, semiorganic polymer of organic radicals attached to silicon containing molecules, such as dimethyl silicone. Silicone elastomers are an excellent material within which to embed the mirrored balls or cylinders, because of their durability with respect to ultraviolet light, among other reasons.
“Thermoplastic” refers to materials with a molecular structure that will soften when heated and harden when cooled. This includes materials such as vinyls, nylons, elastomers, fuorocarbons, polyethylenes, styrene, acrylics, cellulosics, etc.
“Van der Waals force” as used herein refers to an attrative force between atoms or molecules. It can arise because a fluctuating dipole moment in one molecule induces a dipole moment in the other. The two dipole moments then attract.
“Zeta potential,” is the net surface and volume charge that lies within the shear slipping surface resulting from the motion of a body through a liquid. It is an electrical potential that exists across the interface of all solids and liquids. It is also known as the electrokinetic potential. The zeta potential produces an electric dipole moment (field) of a spherical body when it is made from two dielectrically different hemispheres due to the interaction of the sphere with the fluid that it is immersed in.